ANALYSIS OF DYNAMIC FRACTURE-BEHAVIOR OF PARTIALLY-STABILIZED ZIRCONIA AT ELEVATED-TEMPERATURES BY THE METHOD OF CAUSTICS

The validity of the caustic method on fracture problems of partially stabilized zirconia at room and elevated temperatures up to 1200-degrees-C is confirmed, and we investigated the dynamic fracture behavior of this material from pictures taken using the apparatus of caustics together with an ultrahigh-speed camera, Imacon 790. Consequently, it is revealed that dynamic fracture toughness K(Id) abruptly decreases as the testing temperature increases over about 500-degrees-C, and the ratio of K(Id) to static fracture toughness is increased from 2.0 at room temperature to 5.0 at 800-degrees-C. Moreover, it is ascertained that the crack-propagation fracture toughness is increased with the crack velocity at any testing temperature up to 1200-degrees-C, and this tendency is decreased with the rise of temperature in this range. Finally, an example of the visualized acoustic emission (AE) wave is shown. It is revealed that the velocity of this AE wave decreases slightly as the temperature rises, and it coincides with the Rayleigh wave speed of this material.